1. Field of the Invention
The present invention relates to a method for scrambling and/or descrambling FM subcarrier data. More specifically, the present invention relates to a method for scrambling and/or descrambling FM subcarrier data in an FM multiple radio broadcasting system, which scrambles and/or descrambles input data by possessing a random number and the input data in an exclusive OR manner, and relates to a method for generating scramble key data.
2. Description of the Prior Art
It has been proposed to broadcast traffic information with using the FM multiple radio broadcasting system. In order to offer the traffic information to only a member at a charge, data of the traffic information may be scrambled.
On the other hand, a specific scrambling method and descrambling method in a satellite broadcasting system are suggested in, for example, "Technical Condition for Data Broadcasting in Satellite Broadcasting System" published by BROADCASTING TECHNOLOGY DEVELOPMENT CONFERENCE in June, 1993. One example is shown FIG. 1 to FIG. 3.
In scrambling and/or descrambling data in the satellite broadcasting system, an initial value is set in an initial value register included in a PN (Pseudo Noise) signal generation circuit shown in FIG. 1 on the basis of scramble key data. Then, the initial value is modified by an initial value modification circuit shown in FIG. 2, and a modified initial value is set in feedback registers of a PRBS generation circuit shown in FIG. 3. Details are described in page 51 to page 57 of "Technical Condition for Data Broadcasting in Satellite Broadcasting System".
However, the above described scrambling and/or descrambling method of the satellite broadcasting system can not be used in the FM multiple radio broadcasting system because there is a structual difference between a data packet of the data in the satilite broadcasting system and a data packet of the data in the FM multiple radio broadcasting system.